The objective of the proposed research is to improve the sensitivity and selectivity of a catalytic metal electrode for determining glucose in biological fluids. Such improvements could lead to the development of an implantable glucose sensor that could provide opportunities for a much greater degree of control of glucose levels in diabetics than in now possible. Such control would provide improved therapy for one of the world's major health problems. Glucose sensor work using a catalytic metal sensor based upon platinum is currently being performed in our laboratories. Using a newly discovered technique for measurement, a sensor with sufficient accuracy and response time to function as an implantable alarm monitor has been developed. For more demanding applications (e.g., to control the infusion of insulin by a pump), however, improvements in the accuracy of the sensor will be required. One approach involves the use of an electrode material with greater catalytic activity for the electrochemical oxidation of glucose, and/or lesser activity for the oxidation of any endogenous coreactants. Another involves the use of an electrode material that would respond only to endogenous coreactants so that a correction for these coreactants could be made. Work directed towards both of the above goals is proposed.